A unit of effective radiation dosage. It doesn't measure the amount of radiation you were exposed to or how much was absorbed (those are hard to distinguish, by the way), but the relative "effect" of the radiation dose. Some radiation is more harmful than others, and so on, and this must be taken into account. So you could have absorbed a lot of X-rays and suffer the same amount of biological effect as absorbing a lot less energy in alpha particles or something.

A "rem" stands for "roentgen equivalent man," and represents a unit of effect on human (or generally mammalian) tissue. The rem is the unit in the cgs system; the SI unit is the sievert. 1 Sv=100 rem.

You may also be looking for the rock band R.E.M.

A statement in the programming language BASIC that is roughly the same as a comment in C or C++. In other words, the compiler ignores the line - it's there purely for the benefit of a human reader. It works like this -

10 REM This program prints a message out to the user.
20 PRINT "Hello, World!"

REM is a command in the MS-DOS command interpreter frequently used in batch files. REM performs no action. The intent of this command is to supply remarks within the batch file that will be ignored by the computer, but visible to a programmer looking at the file. In effect, REM is batch language syntax for a comment. For example:

REM This line has no effect.

Any parameters to REM will be ignored. However, the exception to this rule is the /? parameter, which, in modern versions of DOS, will display a summary of the command. Therefore, one should not attempt to indicate a comment beginning with /?.

If REM is the first token on a line in DOS's CONFIG.SYS file, that line will be ignored. Therefore, REM also provides a commentary feature in that file. However, this functionality is only available since, I believe, DOS 5.0.